(a) Field of the invention
The present invention relates to a cutter head of a pit-boring machine, and more particularly it pertains to a cutter head of a boring machine which is used in reverse circulation drilling.
(b) Description of the prior art
The so-called reverse circulation drilling technique is employed in the drilling of pits for driving piles in the construction of buildings. Piles for the construction of large buildings are forced to penetrate into the rock stratum which is beneath the soil layer. The cutter heads of a boring machine have heretofore consisted of two types, one of which is intended for the excavation of soil, and the other is for the drilling of rocks. It has been the practice that the boring of the soil layer and rock stratum is carried out by using a cutter head appropriate for the type of material to be excavated.